The present invention relates to a cylindrically-shaped hollow rod, also called concertina, which is closed at one end and is comprised of a shirred tubular casing. The hollow rod includes in its cavity, i.e., in the interior of the bore of the concertina, an integral plug-type closure element which is adjacent to the inside wall of the hollow rod and comprised of an irregularly folded, compressed tubing section. The invention relates also to a process and device for production of the tubular casing. The closure element is also called an end closure.
Hollow rods of this type, which are, for example, made of cellulose hydrate, are used for producing sausages. For filling the cavity of the hollow rod with the sausage meat, the stuffing horn of the sausage stuffing machine is first inserted into the cavity of the hollow rod up to the end of the rod which is closed by the closure element, then the sausage meat is pressed through the stuffing horn into the cavity of the hollow rod. By means of the pressure exerted by the sausage meat, the hollow rod is continuously deshirred. The sausage strand which is thereby formed is divided into a plurality of individual sausages by tying off or twisting.
The first end of the first sausage carries the closure element. This sausage is thrown away, for it usually does not contain a sufficient quantity of sausage meat. For reasons of economy, it is, however, desirable that the sausage meat contained in this first sausage casing can be recovered; therefore, the end closure must be designed such that it can be opened manually without difficulaty, by stripping off the sausage meat. On the other hand, no unintentional opening of the end closure must occur due to the sudden pressure exerted by the sausage meat when the stuffing process starts.
Hollow rods of the type mentioned at the outset are, for example, known from U.S. Pat. No. 3,383,222. In accordance with the teaching of this publication, an end portion of the hollow rod is pulled off perpendicularly to the longitudinal axis by means of a hook-like tool. By a first plunger, the portion of the casing which covers the aperture of the hollow rod is pressed into the interior of the concertina, whereby an adjacent portion of the casing is deshirred and also pressed into the cavity of the hollow rod. Then the first plunger is removed. Subsequently, the portion of the casing, which is now located in the interior of the hollow rod, is pressed against a stop member brought into contact with the end of the hollow rod to be closed, by a second plunger introduced into the opposite end of the hollow rod, and is thus compressed.
This closure element is hardly capable of withstanding the high pressure applied in modern sausage stuffing equipment. Furthermore, it is of an undefined shape, which often leads to non-reproducible results. There is also the risk of unintenionally damaging the inner side of the hollow rod, when the two plungers are introduced. Moreover, the process is relatively expensive because of the numerous individual process steps and the various applicances required.